The concept of speciationhow new species are formed from existing specieswas posed by Darwin in his book On the Origin of Species. The following Websites help in understanding this process as it occurs in populations.
23.1 Defining and Identifying Species
Journey into Phylogenetic Systematics
This online exhibit from the Museum of Paleontology at UC-Berkeley walks you through the basic concepts of cladistics, a field in which biologists study and construct phylogenetic models of the evolution of life. Links lead to the construction of an example phylogenetic tree, as well as many other resources and evolutionary research institutes.
Keywords: cladistics, phylogeny, systematics
23.2 Isolation and Divergence in Sympatry
The diversity of genes within a population is important if a species is to be able to adapt to a changing environment. Without genetic diversity, species are far more likely to become extinct.
Keywords: genetic diversity, extinction, speciation, gene
The Evolution of Reproductive Isolation in Monkeyflowers
Doug Schemske's fascinating work on the genetic and molecular changes that occur during speciation are discussed on this research Website. Many of the concepts are framed as questions, highlighting the "inquiry" nature of biological research.
Keywords: sympatric, speciation
Allopatric vs. Sympatric Speciations
23.3 Isolation and Divergence in Allopatry
This short article compares the relative importance of allopatric speciation to sympatric speciation.
Keywords: speciation, allopatric
This article explains how islands are fertile grounds for allopatric speciation events and discusses the general concepts of island biogeography. The links on the page provide terrific examples of how islands can contribute to speciation events.
Keywords: speciation, allopatric, island biogeography
Robert Fleischer has been able to plot much of the biological history of bird colonization and speciation on the Hawaiian Islands. This article from the Smithsonian Institution describes his research on the distribution of species on the Islands.
Keywords: colonization, speciation, population genetics
Speciation and Hybrid Zones
23.4 Secondary Contact
This is a research article in the Biological Journal of the Linnean Society. It discusses hybrid zones and speciation through two examples of butterfly species. The article is in the PDF format, so an Adobe Acrobat plug-in is required for your browser.
Keywords: hybrid zone, reproductive isolation, natural selection
Most research on reproductive isolation and speciation indicates that these processes may take many generations to occur. This article discusses recent research indicating that isolation and changes in a population's gene pool can occur rapidly under the right circumstances.
Keywords: reproductive isolation, speciation